Here are two mini flyers that came with DJ SS tape releases from 1991:Turntable Psycho Rave no.10 (green flyer) and no.11 (yellow flyer).
Both advertise production label HQ5.
Both sizes fit nicely into the cases, with green being slightly larger.
Apart from these two tape releases by DJ SS, I don't know of any others self-released in 1991.